Mk3 valves, is this guide seals?

Hello, is this caused by leaking guide seals?







The top of both pistons were similar, but not as much flakey build up.

Graeme

More than likely the valve stem-to-guide bore clearance is slopped out enough to let some oil pass by. I have this weird theory that guide seals prevent lubrication from reaching the stem and this makes the guide bores wear quicker. Carbon buildup is just a fact of life with these old motors. Decarbonising was and is considered regular maintenance.

Thanks Danno, I forgot to say these are the inlet valves. The exhaust valves look normal.
Yes, I can see scuff marks on one side of the new valves , makes sense.
And the inlet tract had a strange sticky oil coloured lining, I thought it was air filter oil that had been sucked in?
It could have been engine oil blown back past the bad seating valves?

graeme

The exhaust valves run so hot, all the carbon burns off before it accumulates. The buildup could be a combination of rich fuel mixture AND oil, There is a period when the intake valve is beginning to open as the piston finishes the exhaust stroke when any oil present in the cylinder could be pushed back into the intake tract, so what you have could be a combination of all three of the named sources. The easiest way to check valve guide and stem wear is to disassemble the springs (looks like you've done that) and slide the valve back into the guide almost to the point of it hitting the seat, then try to wiggle it. If it moves very much at all, you likely need new guides at the least.

Intake valves try to pull the oil past the seals/guides when they are open due to the vacuum in the cylinder. Thats why many older engines do not utilize seals on the exh valves. There is no vacuum present in the cylinder when exh valves are open. However, the venturi effect can pull oil past the exh stems and into the exhaust stream. That's why modern engines tend to have seals on Int an Exh valves. But as noted, probably both the seals and guides/valve stems need replacing. Sometimes just new valves and seals will be sufficient. But if there is any wobble at all in the valve when the valve is at normal max lift, it's too much. New seals will not last long if the stem/guide clearance is above spec.